1. Field of the Invention
This invention relates to a DC-DC converter apparatus for converting a D.C. input into a stabilized output of different voltages, and more particularly, to reducing a standby current in the DC-DC converter apparatus when the DC-DC converter apparatus is in a non-operative state.
2. Description of the Related Art
A DC-DC converter apparatus is typically used as a power source of a data processing system for converting a D.C. input into a stabilized D.C. output having an adequate voltage and adequate power capacity to be supplied to a circuitry. A power source section is constructed by a plurality of DC-DC converter apparatuses and each of the DC-DC converter apparatuses supplies electric power to at least one load (i.e., the circuitry). At least one of the DC-DC converter apparatuses may have a main power supply circuit and a supplemental power supply circuit. The main power supply circuit converts a D.C. input into a stabilized D.C. output adequate for the load and supplies the converted D.C. output to the load. The supplemental power supply circuit converts the D.C. input into a plurality of D.C. outputs necessary for the operations of respective sections of the DC-DC converter apparatus and supplies the plurality of D.C. outputs of adequate voltages to the respective sections of the DC-DC converter apparatus. The main power supply circuit and supplemental power supply circuit are each constructed as a DC-DC converter. A D.C. power input to the DC-DC converter apparatus is D.C. power converted from A.C. power supplied from an A.C. power source by an AC-DC converter, for example.
When electric power is supplied to a load, both the main power supply circuit and the supplemental power supply circuit are operating. On the other hand, when no electric power is supplied to the load, that is, when the circuit of the load is not operating, the operation of the main power supply circuit is interrupted but the supplemental power supply circuit is still operating. The reason why the supplemental power supply circuit is still operating even when the main power supply circuit is set in the non-operative state is to set the main power supply circuit in the standby state so that the main power supply circuit can be immediately operated when necessary. Therefore, in the DC-DC converter apparatus, a current for operating the supplemental power supply, that is, a standby current, always flows.
When a large number of DC-DC converter apparatuses are used as the power source section of the apparatus, however, the standby current becomes large and an amount of heat generated in a power distribution unit for supplying D.C. power to the DC-DC converter apparatuses becomes large. Typically, the power distribution unit is constructed of AC-DC converters. If the amount of generated heat becomes large, as described above, however, it becomes necessary to increase the cooling capacity of the power distribution unit. When the amount of generated heat of the power distribution unit becomes larger and the heat of the power distribution unit cannot be sufficiently radiated by natural air-cooling, a cooling fan is used to forcedly cool the power distribution unit, thereby suppressing the heat generation of the power distribution unit.
Thus, in the conventional DC-DC converter apparatus, even if the main power supply circuit is interrupted, an unwanted power caused by a standby current or the sum of the standby currents and the driving current for the cooling fan is consumed. Further, when the cooling fan is driven, noise is generated by the rotation of the fan.